As wireless devices have exploded in popularity, the ability to provide sufficient coverage to more and more users over large areas is more crucial than ever. Current cellular antenna array techniques have reached limiting factors in meeting these demands. As such, there is a growing need to provide wireless coverage with higher capacity in certain regions.
Current standard cellular arrays produce a single azimuth beam with 65-degree or 90-degree beam-width for sectorized cellular coverage. In an urban area, there can exist several densely populated areas, or hot spots, where particularly high capacity of communications are required. In such cases, additional steerable beams with narrow azimuth beam-width can be used to improve capacity in these areas.
One conventional approach for producing several narrow azimuth beams involves use of a Butler matrix with a uniform weight function. However, this approach produces radiation patterns with relatively high sidelobes that waste energy and may cause interference with neighbouring beams. Other approaches use an additional antenna with a relatively large aperture on top of a typical cellular array to produce the narrow beams in a cellular network. This method is undesirable due to limited and expensive real estate on a cellular tower. Furthermore, the narrow beam produced in this manner is often not electronically steerable making this approach only useful in a scenario with fixed geographical density.